1. Field of the Invention
The present invention relates to a fine projection composite structure in which a fine projection such as a semiconductor dot or a semiconductor/metal composite dot both of nanometer scale is formed on a semiconductor substrate, and a fabricating method thereof.
2. Description of the Related Art
An integration rate of a semiconductor device represented by a DRAM is increasing year by year. For instance, the integration rate of a DRAM has been heightened from 16 Mbit to 64 Mbit or 256 Mbit, and further development of a semiconductor device of the integration rate of more than Gbit is under way. Such a high integration of a semiconductor device has been achieved through reduction of a unit element size down to sub-micron order. For miniaturization of the unit size, development in lithography technology has largely contributed. In addition to improvement of lithography technology, improvement of an element structure is also in progress.
Concerning the lithography technology, due to improvement of i-line exposure technique and positive photo-resist, 0.5 .mu.m rule corresponding to 16 Mbit-DRAM is being put into practical use. Further, due to development of the exposure technique using KrF excimer laser which can correspond to 0.25 .mu.m rule, 64 Mbit-DRAM is being mass produced and the practical use of 256 Mbit-DRAM is under way. Further, correspondence to 0.18 .mu.m rule due to improvement of the exposure technique employing KrF excimer laser or development of the exposure technique employing the SOR light is under way. However, the limit of present lithography technology is considered to be about 0.1 .mu.m rule. Therefore, in order to achieve further higher integration, it is desired to be realized in the future a unit element size of nanometer scale.
Further, a quantum-size device is attracting attention as a candidate of future LSI technology. Realization of a new device utilizing a quantum-size effect or a tunnel effect, for example, such as a quantum wire device or a quantum dot device which makes use of a wire or a dot structure of which sectional dimension is at the same degree with a quantum mechanical wavelength of an electron, a resonant tunnelling effect device or a resonant tunnelling element utilizing a quantum well and so on, are being tried.
In order to develop a new device which positively utilizes a quantum effect, a characteristic dimension of an element should not remain in a phase wavelength (0.1 to 1 .mu.m) order, namely in a mesoscopic region, but should be brought into an electron wavelength order (10 to 100 nm), namely in a microscopic region. Further, in order to utilize more effectively a quantum effect device, ultra-miniaturization of the unit element size itself of, for instance, 10 to 100 nm, more preferably less than 10 nm, is required. However, it is far beyond the present lithography technology level.
As described above, research and development of the quantum size device and the like which are expected as candidates of a ultra-high integration semiconductor device or future LSI technology are under way. To materialize such a fine device, a unit element size of nanometer scale is required to be achieved. Therefore, a technology enabling to obtain with reproducibility a semiconductor dot or a semiconductor/metal composite dot, which is necessary for a ultra-high integration semiconductor device or a quantum-size device, is desired to be developed.